Photoflash units, also called flash devices, flash lighting devices etc, of various kinds are commonly used in photography for producing a flash of artificial light to help illuminate a scene, a scene which would otherwise be perceived as underexposed, i.e. too dark, to the viewer of a captured picture of the scene. Other uses of flashes are capturing quickly moving objects or changing the quality of light. Most current flash lighting devices are electronic and have been developed through xenon-based flash devices to state of the art light emitting diode (LED) flash devices. Historically, flashes were produced by means of rather inconvenient arrangements, such as single-use flashbulbs and flammable powders. As a contrast to these historical arrangements, modern cameras often activate connected flash lighting devices automatically, and the rapid technological development of compact pocket cameras, mobile terminals and smart phones has nowadays led to relatively advanced, in-built cameras with very high resolution and adaptable flash devices as a de facto standard with few exceptions.
In order to utilize various commonly used flash lighting devices, camera bodies are according to internationally accepted standards equipped with a so-called hot shoe accessory connector. A flash lighting device may be connected, directly or through an extension cord, to the hot shoe connector. The emission of flash light from the lighting device can be synchronized to an image acquisition by the camera by a synchronization signal received by the lighting device. In prior art camera systems, this synchronization signal is transmitted from the camera to the flash device via its connection to the hot shoe connector.
In modern applications of camera systems and in studio equipment for photography, a remote flash lighting device can be triggered by wireless synchronization, which has been realized using optical, such as infrared, and radio frequency communications to the remote flash device. Radio frequency synchronization typically involves connecting a radio transmitter to the camera body and a radio receiver to the remote flash device. The radio transmitter sends a signal to the radio receiver to activate the remote flash device in synchronization with image acquisition by the camera. For that purpose, radio frequency communication systems may include a transmitter at the remote flash device for sending a confirmation signal back to the camera side radio, indicating that the flash-side radio has successfully activated the flash lighting device in use.
In order for such two-way communication in a camera system to be fully functional and reliable, it is necessary for the camera and for the flash device to comply with standards available. Also their respective external or integrated modules for the execution of communication there between, need to be compatible and to support existing standards with respect to signalling schemes that are in use by different camera and flash device manufacturers on the market. Since standardization available in the field is allowing for deviations with respect to certain more advanced functions, both mechanically and electronically, it is in practice hard or even impossible to satisfy all requirements if complete operability is requested.
Through-the-lens (TTL) flash photographic control typically involves the camera body measuring lighting conditions, such as an amount of energy in the form of light, provided by a flash lighting device during a test firing or preflash of the flash device. The measurement is performed through the lens of the camera. The camera then provides an indication to the flash device connected to the hot shoe connector of the amount of light, i.e. provision of power and timing, to be applied by a main flash during the actual image acquisition procedure. The indication of the amount of light can be made by providing start and stop signals to the flash device via the hot shoe connector.
In another example of TTL flash photographic control, the indication of the amount of light can be made by providing a serial data, via the hot shoe connector to the flash device connected thereto, that includes an adjustment to the amount of light that was provided in the preflash. The flash device in the hot shoe connector can activate a remote flash light by utilizing optical flash pulses, such as visible light or infrared light. The optical pulses can also be used to send TTL power adjustments to the remote flash device. However, according to this control system, the remote lighting devices are not providing any information back to the flash lighting device in the hot shoe connector of the camera body. This system therefore requires that a light emitting device be connected to the hot shoe connector.
Using camera and flash or similar lighting systems presently available on the market means that the choice of camera in practice limits the choice of flash device or related lighting device, or alternatively, in the sense that a flash or lighting device limits the choice of camera. Each manufacturer of cameras advocates its own specific communication protocol for communication with flash devices intended for use with that particular camera. For an amateur photographer who is in possession of a flash device, which cannot be used any longer together with certain camera equipment because of the above mentioned limitation, this may be greatly discouraging. For a professional photographer, or a commercial studio environment collaborating with many different photographers with varying preferences in their choice of camera equipment, this may be a severe limitation. To overcome the limitation, professional studios are typically obliged to be equipped with numerous brands of flash devices, so as to accommodate the needs of any professional photographer, and as a consequence the costs to the studio are substantially increased.
There have been made attempts to overcome the mentioned problem. Flash lighting devices have been available that allow for mechanical substitution of the part in contact with the hot shoe connector of the camera. However, having to modify the lighting devices to be used to various camera bodies is highly undesired. In addition to that, there is no way of overcoming the limitation that use of numerous lighting devices together with one camera is impossible, unless all lighting devices are produced by the same vendor and thus are recommended and fully compatible with the camera equipment in use. When consideration is made to a standard type of studio environment, lighting devices of different types and brands are often hinged near the ceiling of the studio and therefore in practice impossible to adjust or substitute components on, only to be usable together with various cameras.
It is therefore conceivable to assume that a market incentive exists to remove the mentioned limitations one way or the other. However, despite this incentive, and despite prior attempts to overcome problems relating to the limited choice of equipment due to lacking interoperability, there is presently no solution available. It would seem logical to develop and introduce to the market flash devices that are able to simultaneously operate with a variety of different camera types and brands. No such flash devices have yet been developed.